1. Technical Field
The present invention relates to an improved method for producing shelf-stable snack foods and especially low oil snack foods. More specifically, the present invention relates to a method whereby a unique combination of unit operations are used to produce a low-fat potato crisp having organoleptical properties similar to those of traditional fried potato crisps.
2. Description of Related Art
Conventional potato crisp products are prepared by the basic steps of slicing peeled, raw potatoes, water washing the slices to remove surface starch, and frying the potato slices in hot oil until a moisture content of about 1-2% by weight is achieved. The fried slices can then be salted or seasoned and packaged.
Raw potato slices normally have a moisture content from about 75% to about 85% by weight depending on the type of potato and the environmental growing conditions. When potato slices are fried in hot oil, the moisture present boils. This results in burst cell walls and the formation of holes and voids which allow for oil absorption into the potato slices yielding oil contents ranging from about 30% to about 45% by weight.
The oil content of potato crisps is important for many reasons. Most important is its contribution to the overall organoleptic desirability of potato crisps, however, from the standpoint of good nutrition, it is desirable to maintain a low level of oil or fat in potato crisps. Many health conscious consumers desire a low fat alternative to the traditional fried crisp having minimal taste differences from the fried product.
Further, a high oil content renders the crisps greasy or oily and hence less desirable to the consumer. Numerous attempts have been made in the prior art to reduce the oil content in potato crisps. Many attempts involve thermally processing the potato slices in an oven or a microwave to avoid the addition of oil to the potato crisp.
For example, U.S. Pat. No. 5,292,540 claims a process for preparing potato crisps by first pre-baking the potato slices at a temperature of between about 121° C. to about 260° C. (250° F. to 500° F.) to remove about 50% to about 80% of the moisture in the slice prior to microwave heating the potato slices.
Similarly, U.S. Pat. Nos. 5,180,601; 5,202,139; and 5,298,707 all relate to a method and apparatus for producing fat-free snack crisps. For example, U.S. Pat. No. 5,298,707 discloses a first intensive microwave pre-baking step that reduces the moisture content in the potato to about 25% to about 30% by weight. The '707 patent employs a special intermittent microwave field provided by a meandering wave guide and a special conveyor belt to reduce the problems of hard surface and texture. However, according to U.S. Pat. No. 5,676,989, the approach disclosed in U.S. Pat. No. 5,298,707, still produces an undesirable, relatively dense, hard crisp. Similarly, nearly all of the prior art processes result in a low fat snack food having organoleptical properties far less desirable than the fried potato crisp counterpart. Thus, none of the prior art solutions have succeeded in mimicking the taste and texture of fried potato crisps.
Consequently, a need exists to provide an economical method for making reduced oil potato crisps having desirable organoleptical properties similar to traditional potato crisps.